Conventional window and door manufacturers have commonly used wood and metal components in forming structural members. Commonly, residential windows are manufactured from milled wood products or extruded aluminum parts that are assembled with glass to form typically double hung or casement units. Wood windows while structurally sound, useful and well adapted for use in many residential installations, can deteriorate under certain circumstances. Wood windows also require painting and other periodic maintenance. Wooden windows also suffer from cost problems related to the availability of suitable wood for construction. Clear wood products are slowly becoming more scarce and are becoming more expensive as demand increases. Metal components are often combined with glass and formed into single unit sliding windows. Metal windows typically suffer from substantial energy loss during winter months.
Extruded thermoplastic materials have also been used as non-structural components in window and door manufacture. Filled and unfilled thermoplastics have been extruded into useful seals, trim, weatherstripping, coatings and other window construction components. Thermoplastic materials such as polyvinyl chloride have been combined with wood members in manufacturing PERMASHIELD.RTM. brand windows manufactured by Andersen Corporation for many years. The technology disclosed in Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,883, have been utilized in the manufacturing of plastic coatings or envelopes on wooden or other structural members. Generally, the cladding or coating technology used in making PERMASHIELD.RTM. windows involves extruding a thin polyvinyl chloride coating or envelope surrounding a wooden structural member.
Polyvinyl chloride has been combined with wood to make extruded materials. Such materials have successfully been used in the form of a structural member that is a direct replacement for wood. These extruded materials have sufficient modulus, compressive strength, coefficient of thermal expansion to match wood to produce a direct replacement material. Typical composite materials have achieved a modulus greater than about 500,000 psi acceptable COTE, tensile strength, compressive strength, etc. to be useful. Deaner et al., U.S. Pat. Nos. 5,406,768 and 5,441,801, U.S. Ser. Nos. 08/224,396 abandoned in favor of 08/326,481 which was abandoned in favor of 08/587,828 which is now pending; U.S. patent application Ser. No. 08/326,480 now pending; as well as U.S. patent application Ser. No. 08/224,399 now issued U.S. Pat. No. 5,486,553; U.S. patent application Ser. No. 08/326,472 now U.S. Pat. No. 5,539,027; U.S. patent application Ser. No. 08/326,479 now U.S. Pat. No. 5,497,594; and U.S. patent application Ser. No. 08/372,101 which has issued as U.S. Pat. No. 5,518,677 disclose a PVC/wood fiber composite that can be used as a high strength material in a structural member. This PVC/fiber composite has utility in many window and door applications.
A substantial and continuing need exists to provide a improved composite material (using polymers having no chloride containing monomer components) that can be made of thermoplastic polymer and wood fiber. The composite can be made with an optional, intentional recycle of a waste stream. A further need exists for a composite material that can be extruded into a shape that is a direct substitute for the equivalent milled shape in a wooden or metal structural member. A thermoplastic with fiber compatibility, good thermal properties and good structural or mechanical properties is required. This need also requires a composite with a coefficient of thermal expansion that approximates wood, that can be extruded into reproducible stable dimensions, a high modulus, a high tensile strength, a high compressive strength, a low thermal transmission rate, an improved resistance to insect attack and rot while in use and a hardness and rigidity that permits sawing, milling, and fastening retention comparable to wood members. Further, companies manufacturing window and door products have become significantly sensitive to waste streams produced in the manufacture of such products. Substantial quantities of wood waste including wood trim pieces, sawdust, wood milling by-products, recycled thermoplastic materials, has caused significant expense to window manufacturers. Commonly, these materials are either burned for their heat value in electrical generation or are shipped to qualified landfills for disposal. Such waste streams are contaminated with substantial proportions of hot melt and solvent-based adhesives, waste thermoplastic, paint, preservatives, and other organic materials. A substantial need exists to find a productive environmentally compatible use for such waste streams to avoid returning the materials into the environment in an environmentally harmful way. A composite that can be made with properties of these streams can be an advantage.